Prior art patent document published WO 2004/052077 A2 discloses a pressure reducer for a heliox mixture compressed in a cylinder. The pressure reducer serves also as shut-off valve and is kept in a shut-off position by a stem that urges the piston and the closure element thereof against the seat. A control knob disposed on the top of the device actuates the position of the stem so that upon rotation of the control knob, the stem can release the piston and open the device. The gas can then flow and is regulated by means of the piston forming a low-pressure chamber that regulates the opening through the seat. The control knob comprises a locking mechanism that prevents the device to be turned off after the flow begins. The pressure reducer can only be reset for reuse by a service entity. This pressure reducer is interesting in that it comprises a single shut-off device that fulfil the function of a shut-off valve and also a function of regulation when the pressure reducer is opened. The release of the device requires however a sophisticated and room consuming arrangement on top of the pressure reducer.
Prior art patent document published U.S. Pat. No. 6,047,727 discloses a valve assembly for gas cylinder. This valve assembly comprises a pressure reducer with a piston that is resiliently biased by a plurality of stacked cone disk springs, commonly named Belleville washers. A series of first cone disk springs is resting on a pair of second cone disk springs of a larger diameter. These two larger springs are arranged such that an adjustable cap member can act on the position of these springs, thereby influencing the pre-stress of the series of first cone disk springs. This teaching provides an interesting adjustment solution for a pressure reducer. It however does not provide any solution for holding the pressure reducer in a shut-off state and for releasing it.